阅读说明：本技术 一种无人机双余度前轮转弯伺服系统 (Unmanned aerial vehicle dual-redundancy front wheel turning servo system ) 是由 刘鹏 李清 王丹阳 周卫卫 衡春影 于 2021-07-28 设计创作，主要内容包括：本发明提供了一种无人机双余度前轮转弯伺服系统,该双余度前轮转弯伺服系统包括伺服控制器和转弯伺服机构,伺服控制器和转弯伺服机构中均有主、备两个通道,正常状态下,主通道工作,备份通道随动,通过伺服控制器的故障监测模块,当监测到主通道发生故障时,将工作通道切换为备份通道,主通道随动。当监测到备份通道也发生故障时,则将主、备份通道全部切除,并上报给飞控计算机,该模式有效提高了伺服系统的可靠性,结合机械结构研发,使无人机用全电式双余度前轮转弯伺服系统具有可靠性高、运动精度高、维护方便的特点,满足了无人机可靠性、维修性、安全性及全电化的需求。(The invention provides a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle, which comprises a servo controller and a turning servo mechanism, wherein the servo controller and the turning servo mechanism are respectively provided with a main channel and a standby channel, the main channel works and the standby channel follows up in a normal state, and when the main channel is monitored to have a fault through a fault monitoring module of the servo controller, the working channel is switched to the standby channel and the main channel follows up. When the backup channel is monitored to have a fault, the main channel and the backup channel are completely cut off and reported to the flight control computer, the mode effectively improves the reliability of the servo system, and the full-electric dual-redundancy front-wheel steering servo system for the unmanned aerial vehicle is researched and developed by combining a mechanical structure, has the characteristics of high reliability, high motion precision and convenience in maintenance, and meets the requirements of the unmanned aerial vehicle on reliability, maintainability, safety and full electrification.)

1. A double-redundancy front wheel turning servo system of an unmanned aerial vehicle is characterized by comprising a servo controller and a turning servo mechanism, wherein the servo controller comprises a fault monitoring module and a main control channel and a backup control channel which are completely the same, the main control channel and the backup control channel both comprise a control circuit and a driving circuit, the control circuit is a control core of the turning servo system, is communicated with a flight control computer, receives a sent control instruction, receives and uploads an actual deflection angle of an output shaft of the turning servo mechanism sent by the turning servo mechanism, compares the deflection angle of the output shaft of the turning servo mechanism with the control instruction, and outputs a PWM signal to the driving circuit through closed-loop operation; the driving circuit adjusts the voltage output to the turning servo mechanism according to the PWM signal, and finally changes the rotating speed of an output shaft of the turning servo mechanism;

the turning servo mechanism comprises a transmission mechanism and two identical executing channels of a main executing channel and a backup executing channel, wherein the main executing channel and the backup executing channel both comprise brushless motors and angle sensors, the brushless motors are power elements of the turning servo mechanism, and the angle sensors are angle detection elements of an output shaft of the turning servo mechanism and are used for transmitting the collected deflection angles of the output shaft of the turning servo mechanism to a control circuit of a servo controller; the main execution channel brushless motor and the backup execution channel brushless motor are both connected with the transmission mechanism, and the rotation motion of the brushless motors is transmitted to the output shaft of the bending servo mechanism.

2. The dual-redundancy front-wheel steering servo system of the unmanned aerial vehicle as claimed in claim 1, wherein the control circuit of each control channel in the servo controller comprises an RVDT decoding circuit, an AD chip, a communication interface circuit and a main control chip, the RVDT decoding circuit is connected with the angle sensor in the channel, receives the deflection angle analog signal of the output shaft of the steering servo mechanism collected by the angle sensor and transmits the deflection angle analog signal to the AD chip, the AD chip converts the analog signal into a digital signal and transmits the digital signal to the main control chip, the main control chip communicates with the flight control computer through the communication interface circuit, receives the control command, compares the deflection angle with the control command, and outputs a PWM signal to the driving circuit through closed-loop operation.

3. The dual-redundancy front wheel steering servo system for the unmanned aerial vehicle of claim 1, wherein a driving circuit of each control channel in the servo controller comprises a power switch and a motor driving module, the power switch is controlled by a fault monitoring module to be turned on and off, and receives a PWM signal when being turned on and sends the PWM signal to the motor driving module; and the motor driving module adjusts the voltage output to the turning servo mechanism according to the PWM signal, and finally changes the rotating speed of an output shaft of the turning servo mechanism.

4. The dual-redundancy front-wheel steering servo system of the unmanned aerial vehicle as claimed in claim 1, wherein the fault monitoring module in the servo controller mainly completes fault monitoring functions through a CPLD chip, including main control chip monitoring, RVDT operating state monitoring, open loop monitoring, stall monitoring and hall monitoring, the main control chip outputs the results of internal monitoring to the CPLD chip through an IO port, the CPLD chip generates fault signals through logic operation, and outputs the fault signals to power switches of driving circuits of the main and backup control channels, thereby realizing switching of the main and backup channels.

5. The dual-redundancy front-wheel steering servo system for unmanned aerial vehicles according to claim 1, wherein the servo controller further comprises a power supply unit, and the power supply unit is used for converting an external power supply voltage into voltages required by each element in the steering servo system.

6. The dual-redundancy front wheel steering servo system for the unmanned aerial vehicle as claimed in claim 1, wherein the steering servo mechanism (1) is mounted on an unmanned aerial vehicle undercarriage (2), an output shaft of the steering servo mechanism is fixedly connected with a rocker arm, the rocker arm is rotatably connected with one end of a connecting rod (4), the other end of the connecting rod (4) is rotatably connected with a front wheel rotating shaft (3), and the rotation output by the steering servo mechanism is converted into the rotation of the front wheel rotating shaft (3) through the connecting rod (4) so as to drive the front wheel to deflect.

7. The dual-redundancy front wheel steering servo system for the unmanned aerial vehicle of claim 6, wherein the distance from the axis of the output shaft (13) of the steering servo mechanism to the connecting rod (4) is equal to the distance from the axis of the front wheel rotating shaft (3) to the connecting rod (4), and the connecting line between the axis of the output shaft (13) of the steering servo mechanism and the connecting rod (4) is parallel to the connecting line between the axis of the front wheel rotating shaft (3) and the connecting rod (4).

8. The dual-redundancy front wheel steering servo system of the unmanned aerial vehicle according to claim 1, wherein the transmission mechanism of the steering servo mechanism comprises a harmonic reducer and a steering servo mechanism output shaft (13), the output shaft of a main channel brushless motor (5) in a main execution channel is fixedly connected with a main channel pinion (7), the output shaft of a backup channel brushless motor (6) in a backup execution channel is fixedly connected with a backup channel pinion (8), the main channel pinion (7) and the backup channel pinion (8) are meshed with a large gear (9) positioned between the main channel pinion and the backup channel pinion, the main channel pinion (7) or the backup channel pinion (8) drives the large gear (9) to rotate when rotating, the large gear (9) is fixedly connected with a cam (10) of the harmonic reducer, the cam (10) is flexibly connected with a harmonic flexible wheel (11), the harmonic flexible wheel (11) is fixedly connected with the steering servo mechanism output shaft (13) and is matched with a harmonic rigid wheel (12), the harmonic rigid gear (12) is used as a partial shell of the turning servo mechanism and is a fixed element, and the high-speed rotation of the cam (10) is converted into the low-speed rotation of the harmonic flexible gear (11) through the interaction of the cam (10), the harmonic flexible gear (11) and the harmonic rigid gear (12), so that the output shaft (13) of the turning servo mechanism is driven to rotate at a low speed.

9. The dual-redundancy front-wheel steering servo system of the unmanned aerial vehicle of claim 8, the turning servo mechanism output shaft (13) is coaxial with the harmonic flexible gear (11) and the harmonic rigid gear (12), a primary sensor gear (14) is fixed at one end of the turning servo mechanism output shaft (13) in the turning servo mechanism shell, the primary sensor gear (14) is meshed with a main channel secondary sensor gear (15) and a backup channel secondary sensor gear (16) on two sides, the main channel secondary sensor gear (15) is fixedly connected with a main channel angle sensor (17), the backup channel secondary sensor gear (16) is fixedly connected with a backup channel angle sensor (18), so that the main lane angle sensor (17) or the backup lane sensor (18) detects the rotation angle of the output shaft (13) of the turn servo.

10. The unmanned aerial vehicle dual-redundancy front wheel turning servo system according to claim 6, wherein the connecting rod (4) comprises an external thread connecting rod (19), an internal thread connecting rod (20) and a locking nut (21), a pin hole is machined at one end of the external thread connecting rod (19), a thread rod section with an external thread is machined at the other end of the external thread connecting rod, a pin hole is machined at one end of the internal thread connecting rod (20), a thread hole with an internal thread is formed at the other end of the internal thread connecting rod, and the thread rod section of the external thread connecting rod (19) is in thread fit with the thread hole of the internal thread connecting rod (20); the locking nut (21) is sleeved on the threaded rod section of the external threaded connecting rod (19), and the locking nut and the internal threaded connecting rod (20) are fastened to prevent loosening by screwing to the end of the internal threaded connecting rod.

Technical Field

The invention belongs to the technical field of unmanned aerial vehicles, and particularly relates to a dual-redundancy front wheel steering servo system of an unmanned aerial vehicle.

Background

The front wheel steering is a main mode for ground turning of large and medium-sized unmanned aerial vehicles, and the front wheel steering also plays a role in correcting the course of the unmanned aerial vehicle during takeoff and landing. The front wheel turning mechanism is an actuating mechanism for realizing front wheel steering, and a large amount of statistics shows that more than 50% of safety accidents occur in the takeoff and landing stages of the airplane, so that the reliability of the front wheel turning mechanism plays an important role in the success or failure of the unmanned aerial vehicle in flying. At present, a large and medium-sized unmanned aerial vehicle generally adopts a hydraulic front wheel turning mechanism, the size and the weight of the unmanned aerial vehicle are large, the risk of oil leakage and air leakage exists, and the maintenance and the repair are complex.

Therefore, it is necessary to provide a front wheel steering servo system to meet the requirements of high reliability, high motion precision, convenient maintenance and the like.

Disclosure of Invention

In order to overcome the defects in the prior art, the inventor carries out intensive research, an unmanned aerial vehicle front wheel turning servo system with high reliability, convenience in installation and high transmission precision is provided, the dual-redundancy front wheel turning servo system comprises a servo controller and a turning servo mechanism, a main channel and a backup channel are arranged in the servo controller and the turning servo mechanism, the main channel works under a normal state, the backup channel follows up, a fault monitoring module of the servo controller switches the working channel into the backup channel when the main channel is monitored to have a fault, and the main channel follows up. When the backup channel is monitored to have a fault, the main channel and the backup channel are completely cut off and reported to the flight control computer, the mode effectively improves the reliability of the servo system, and the full-electric dual-redundancy front-wheel steering servo system for the unmanned aerial vehicle is researched and developed by combining a mechanical structure, has the characteristics of high reliability, high motion precision and convenience in maintenance, and meets the requirements of the unmanned aerial vehicle on reliability, maintainability, safety and full electrification.

The technical scheme provided by the invention is as follows:

a double-redundancy front wheel turning servo system of an unmanned aerial vehicle comprises a servo controller and a turning servo mechanism, wherein the servo controller comprises a fault monitoring module and two control channels which are completely the same as a main control channel and a backup control channel, the main control channel and the backup control channel both comprise a control circuit and a driving circuit, the control circuit is a control core of the turning servo system, is communicated with a flight control computer, receives a sent control instruction, receives and uploads an actual deflection angle of an output shaft of the turning servo mechanism sent by the turning servo mechanism, compares the deflection angle of the output shaft of the turning servo mechanism with the control instruction, and outputs a PWM signal to the driving circuit through closed-loop operation; the driving circuit adjusts the voltage output to the turning servo mechanism according to the PWM signal, and finally changes the rotating speed of an output shaft of the turning servo mechanism;

the turning servo mechanism comprises a transmission mechanism and two identical executing channels of a main executing channel and a backup executing channel, wherein the main executing channel and the backup executing channel both comprise brushless motors and angle sensors, the brushless motors are power elements of the turning servo mechanism, and the angle sensors are angle detection elements of an output shaft of the turning servo mechanism and are used for transmitting the collected deflection angles of the output shaft of the turning servo mechanism to a control circuit of a servo controller; the main execution channel brushless motor and the backup execution channel brushless motor are both connected with the transmission mechanism, and the rotation motion of the brushless motors is transmitted to the output shaft of the bending servo mechanism.

The double-redundancy front wheel steering servo system of the unmanned aerial vehicle has the following beneficial effects:

(1) the invention provides a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle, in order to improve the reliability, a servo controller is designed for redundancy, one servo controller comprises a fault monitoring module and two completely identical control channels, namely a main control channel and a standby control channel, each control channel comprises a control circuit and a driving circuit, all the control channels are completely isolated and do not interfere with each other, when the main channel works, the standby channel does not work, and when the main channel fails, the standby channel is switched on;

(2) the invention provides a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle, which is designed for improving reliability and redundancy of a turning servo mechanism, wherein one turning servo mechanism comprises a transmission mechanism and two identical execution channels, wherein each execution channel comprises a motor and an angle sensor (RVDT), the execution channels are completely isolated and do not interfere with each other, when the main channel works, a backup channel does not work, and when the main channel breaks down, the backup channel is switched on;

(3) in order to improve the motion precision, an angle sensor (RVDT) in a servo mechanism is connected with an output shaft of a turning servo mechanism through a gear pair, the gear pair is made of fluoroplastic, a gear made of the material has a self-lubricating effect, and a positive deviation tooth thickness tolerance is adopted, so that a transmission gap is eliminated;

(4) the invention provides a dual-redundancy front wheel steering servo system of an unmanned aerial vehicle.

Drawings

FIG. 1 is a schematic diagram of a module composition of a dual-redundancy front-wheel steering servo system of an unmanned aerial vehicle according to the present invention;

FIG. 2 is a schematic diagram showing a module composition of a servo controller in a dual-redundancy front-wheel steering servo system of an unmanned aerial vehicle according to the present invention;

FIG. 3 is an installation schematic diagram of a turning servo mechanism in a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle according to the invention;

FIG. 4 is a schematic structural diagram of a turning servo mechanism in a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle according to the present invention;

FIG. 5 is a schematic diagram of cam positioning in a dual-redundancy front-wheel steering servo system of an unmanned aerial vehicle according to the present invention;

fig. 6 is a schematic structural diagram of a connecting rod in a dual-redundancy front wheel steering servo system of an unmanned aerial vehicle.

Description of the reference numerals

1-a turn servo; 2-unmanned landing gear; 3-front wheel shaft; 4-a connecting rod; 5-main channel brushless motor; 6-backup channel brushless motor; 7-main channel pinion; 8-backup tunnel pinion; 9-a bull gear; 10-a cam; 11-harmonic flexspline; 12-harmonic rigid wheel; 13-a turning servo output shaft; 14-primary sensor gear; 15-primary channel secondary sensor gear; 16-backup tunnel secondary sensor gear; 17-a main channel angle sensor; 18-backup lane angle sensor; 19-an externally threaded connecting rod; 20-an internal threaded rod; 21-a lock nut; 24-a first small bearing; 25-a second small bearing; 26-a first sleeve; 27-second sleeve.

Detailed Description

The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

As shown in fig. 1, the invention provides a dual-redundancy front wheel turning servo system of an unmanned aerial vehicle, which comprises a servo controller and a turning servo mechanism, wherein the servo controller comprises a fault monitoring module and two identical control channels, namely a main control channel and a backup control channel, the main control channel and the backup control channel both comprise a control circuit and a drive circuit, the control circuit is a control core of the turning servo system, is communicated with a flight control computer, receives a sent control instruction, receives and uploads an actual deflection angle of an output shaft of the turning servo mechanism sent by the turning servo mechanism, compares the deflection angle of the output shaft of the turning servo mechanism with the control instruction, and outputs a PWM signal to the drive circuit through closed-loop operation; and the driving circuit adjusts the voltage output to the turning servo mechanism according to the PWM signal, and finally changes the rotating speed of an output shaft of the turning servo mechanism. When the backup control channel driving circuit works normally, the power switch of the main control channel driving circuit is turned on, and the power switch of the backup control channel driving circuit is turned off. When the fault monitoring module monitors that the main channel has a fault, the power switch of the main control channel driving circuit is closed, and the power switch of the backup control channel driving circuit is opened, so that the switching of the main channel and the backup channel is realized.

The turning servo mechanism comprises a transmission mechanism and two identical executing channels of a main executing channel and a backup executing channel, wherein the main executing channel and the backup executing channel both comprise a brushless motor and an angle sensor (RVDT), the brushless motor is a power element of the turning servo mechanism, and the angle sensor is an angle detection element of an output shaft of the turning servo mechanism and is used for transmitting the collected deflection angle of the output shaft of the turning servo mechanism to a control circuit of a servo controller. In the main and backup execution channels, the two motors and the angle sensor are completely isolated and do not interfere with each other. The main execution channel brushless motor and the backup execution channel brushless motor are both connected with the transmission mechanism, and the rotation motion of the brushless motors is transmitted to the output shaft of the bending servo mechanism.

In the invention, the main control channel and the main execution channel are connected to form a main channel, and the backup control channel and the backup execution channel are connected to form a backup channel. And the fault monitoring module monitors the fault of the whole main channel or the backup channel during monitoring.

As shown in fig. 2, the control circuit of each control channel in the servo controller includes an RVDT decoding circuit, an AD chip, a communication interface circuit, and a main control chip (DSP), the RVDT decoding circuit is connected to the angle sensor in the channel, receives the deflection angle analog signal of the output shaft of the turning servo mechanism collected by the angle sensor and transmits the deflection angle analog signal to the AD chip, the AD chip converts the analog signal into a digital signal and transmits the digital signal to the main control chip, and the main control chip communicates with the flight control computer through the communication interface circuit, receives the control instruction, compares the deflection angle with the control instruction, and outputs a PWM signal to the driving circuit through closed-loop operation.

The drive circuit of each control channel in the servo controller comprises a power switch and a motor drive module, wherein the power switch is regulated and controlled by a fault monitoring module to be switched on and switched off, and receives a PWM (pulse width modulation) signal when the power switch is switched on and sends the PWM signal to the motor drive module; and the motor driving module adjusts the voltage output to the turning servo mechanism according to the PWM signal, and finally changes the rotating speed of an output shaft of the turning servo mechanism.

The fault monitoring module mainly completes fault monitoring functions through a CPLD chip, including main control chip (DSP) monitoring, RVDT working state monitoring, open loop monitoring, stall monitoring and Hall monitoring, specifically, the DSP outputs an internal monitoring result to the CPLD chip through an IO port, the CPLD chip generates a fault signal through logic operation and outputs the fault signal to power switches of a main control channel driving circuit and a backup control channel driving circuit, and switching of a main channel and a backup channel is realized. For example, when a failure of the main channel is monitored, the CPLD chip outputs a main channel failure signal to the power switch of the main channel to turn off the main channel, and outputs the signal to the power switch of the backup channel through the inverter to turn on the backup channel.

Specifically, the main control chip (DSP) monitors, the DSP periodically sends a self-checking instruction, and if the self-checking fails, the DSP is considered to be in fault;

monitoring the working state of the RVDT, monitoring the output voltage of the RVDT, and if the output voltage exceeds a set range, determining that the RVDT fails;

open loop monitoring, wherein the DSP compares the instruction with position feedback, and when the difference between the instruction and the feedback is greater than 1/4 of the full stroke and the duration time exceeds 1s, the DSP determines to be open loop;

monitoring the stalling, namely monitoring a Hall signal of the steering servo mechanism, calculating the rotating speed of the motor according to the Hall signal, and considering that the motor stalls when the DSP control quantity is detected to be greater than a set threshold value and the rotating speed of the motor is 0 and continuously exceeds 500 ms;

and (4) Hall monitoring, wherein if the detected Hall is all 1 or all 0, the Hall signal is considered to be in fault.

Further, the servo controller further comprises a power supply unit, and the power supply unit is used for converting an external power supply voltage into a voltage required by each element in the turning servo system. In the invention, the servo controller can be integrated into an independent circuit board and electrically connected with the turning servo mechanism.

As shown in fig. 3, turn servo 1 passes through the connecting piece and installs on unmanned aerial vehicle undercarriage 2 as the screw, and turn servo's output shaft links firmly with the rocking arm, and the rocking arm rotates with the one end of connecting rod 4 to be connected, and the other end of connecting rod 4 rotates with front wheel pivot 3 to be connected, turns into the rotation of front wheel pivot 3 through connecting rod 4 with the rotation of turning servo output, and then drives the front wheel and deflect. The distance from the axis of the turning servo mechanism output shaft 13 to the connecting rod 4 is equal to the distance from the axis of the front wheel rotating shaft 3 to the connecting rod 4, and the connecting line of the axis of the turning servo mechanism output shaft 13 and the connecting point of the connecting rod 4 is parallel to the connecting line of the axis of the front wheel rotating shaft 3 and the connecting point of the connecting rod 4.

As shown in fig. 4a to 4c, in the turn servo, the transmission mechanism includes a harmonic reducer and a turn servo output shaft 13, the output shaft of the main channel brushless motor 5 in the main execution channel is fixedly connected with the main channel pinion 7, the output shaft of the backup channel brushless motor 6 in the backup execution channel is fixedly connected with the backup channel pinion 8, the main channel pinion 7 and the backup channel pinion 8 are engaged with the large gear 9 located therebetween, the main channel pinion 7 or the backup channel pinion 8 rotates to drive the large gear 9 to rotate, the large gear 9 is fixedly connected with the cam 10 of the harmonic reducer, the cam 10 is flexibly connected with the harmonic flexible gear 11, the harmonic flexible gear 11 is fixedly connected with the turn servo output shaft 13 and is matched with the harmonic rigid gear 12, the harmonic rigid gear 12 is used as a partial shell of the turn servo and is a stationary element, and the high-speed rotation of the cam 10 is converted into the low-speed rotation of the harmonic flexible gear 11 through the interaction of the cam 10, the harmonic flexible gear 11 and the harmonic rigid gear 12 And further drives the output shaft 13 of the turning servo mechanism to rotate at a low speed.

The turning servo mechanism output shaft 13 is coaxial with the harmonic flexible gear 11 and the harmonic rigid gear 12, a primary sensor gear 14 is fixed at one end of the turning servo mechanism output shaft 13, which is located in a turning servo mechanism shell, the primary sensor gear 14 is meshed with a main channel secondary sensor gear 15 and a backup channel secondary sensor gear 16 on two sides, the main channel secondary sensor gear 15 is fixedly connected with a main channel angle sensor 17, and the backup channel secondary sensor gear 16 is fixedly connected with a backup channel angle sensor 18, so that the main channel angle sensor 17 or the backup channel sensor 18 detects the rotating angle of the turning servo mechanism output shaft 13.

In order to ensure the accurate output position of the front wheel turning servo mechanism 1, the rotation angle of the output shaft 13 of the turning servo mechanism detected by the angle sensors (17, 18) of the main execution channel and the backup execution channel must be accurate. In a conventional gear transmission, backlash is necessary to ensure lubrication, but the presence of backlash adversely affects the accuracy of the rotation angle. In order to eliminate the backlash, the materials of the primary sensor gear 14 and the main and backup secondary sensor gears (15, 16) are replaced by fluoroplastics, and the fluoroplastics have a self-lubricating effect compared with the traditional metal material, so that the backlash is eliminated by adopting positive deviation tooth thickness tolerance while the lubrication is ensured.

As shown in fig. 5, both ends of the turning servo output shaft 13 are fixed to the turning servo housing by a first large bearing 22 and a second large bearing 23. In order to ensure the axial positioning of the cam 10, the cam 10 is fixed to the turning servo output shaft 13 through a first small bearing 24 and a second small bearing 25, a first sleeve 26 is sleeved on the turning servo output shaft 13 between the first small bearing 24 and the second small bearing 25, a second sleeve 27 is sleeved on the turning servo output shaft 13 between the second small bearing 25 and the second large bearing 23, the first small bearing 24 abuts against a shaft shoulder of the turning servo output shaft 13, one side of the cam 10 is axially positioned, the second sleeve 27 abuts against the second large bearing 23, and the other side of the cam 10 is axially positioned.

As shown in fig. 6, the connecting rod 4 includes an external thread connecting rod 19, an internal thread connecting rod 20 and a locking nut 21, one end of the external thread connecting rod 19 is processed with a pin hole, the other end is a threaded rod section processed with an external thread, one end of the internal thread connecting rod 20 is processed with a pin hole, the other end is a threaded hole provided with an internal thread, and the threaded rod section of the external thread connecting rod 19 is in threaded fit with the threaded hole of the internal thread connecting rod 20; the locking nut 21 is sleeved on the threaded rod section of the external threaded connecting rod 19, and the locking nut and the internal threaded connecting rod are fastened by screwing to the end 20 of the internal threaded connecting rod to realize looseness prevention.

Further, the thread pitches of the external thread connecting rod 19, the internal thread connecting rod 20 and the locking nut 21 are all fine threads with the thread pitch of 0.75mm, so that the length of the connecting rod 4 can be finely adjusted, and the front wheel turning servo mechanism 1 is convenient to mount.

Further, a lead seal thread hole is processed on the wall surface of the thread hole side of the internal thread connecting rod 20, a lead seal thread hole is processed on the wall surface of the locking nut 21, after the locking nut 21 is screwed to the end of the internal thread connecting rod 20, the same section of lead seal thread penetrates through the lead seal thread holes of the internal thread connecting rod 20 and the locking nut 21, the internal thread connecting rod 20 and the locking nut 21 are fixedly connected, and the looseness prevention between the external thread connecting rod 19 and the internal thread connecting rod 20 is achieved.

In this embodiment, the motion transmission mode of the front wheel steering servo mechanism is as follows: a main channel brushless motor 5 drives a main channel pinion 7 to rotate, the main channel pinion 7 drives a gearwheel 9 to rotate, the gearwheel 9 is fixedly connected with a harmonic reducer cam 10, a harmonic rigid gear 12 is fixed and fixed, and a harmonic flexible gear 11 is fixedly connected with a turning servo mechanism output shaft 13, so that the rotation of the motor with high speed and small torque is converted into the rotation of low speed and large torque of the output shaft through a harmonic reducer. Meanwhile, a primary sensor gear 14 is fixed on the output shaft 13 of the turning servo mechanism, the primary sensor gear 14 is meshed with a main channel secondary sensor gear 15, and the main channel secondary sensor gear 15 is fixedly connected with a main channel angle sensor 17, so that the main channel angle sensor 17 detects the rotation angle of the output shaft 13.

When the main channel brushless motor 5 and the main channel angle sensor 17 work, the power switch of the backup channel driving circuit is turned off, so that the backup channel brushless motor 6 does not work, and when the main channel brushless motor 5 and/or the main channel angle sensor 17 break down, the backup channel brushless motor 6 and the backup angle sensor 18 are electrified to ensure that the front wheel turning servo mechanism 1 works normally.

The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.